/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineMessageInterface.h
Message header obtained via EnumerateMessages Represents an inbox message that can be downloaded
class FOnlineMessageHeader
FString
FromName
Name of user that sent the message
FUniqueNetIdRef
FromUserId
Unique id of user that sent the message
FUniqueMessageI...
MessageId
Unique id of the message. Needed to download the message payload
FString
TimeStamp
UTC timestamp when message was sent
FString
Type
Type of message